Most electronic-intelligent products work according to the commands input by an operator. The keyboard is one of the most popular input devices for electronic-intelligent products such as notebook computers, portable TVs, cell phones, and personal digital assistants (PDAs).
FIG. 1 illustrates a cross-sectional view of a piezoelectric structure within a prior art keyboard. Typically, a keyboard is composed of a plurality of keycaps and a piezoelectric structure beneath the keycaps, wherein the piezoelectric device comprises at least one elastic element 101, an upper flexible printed circuit 103, a separating sheet 105, and a bottom flexible printed circuit 107. The separating sheet 105 separates the upper flexible printed circuits 103 and the bottom flexible printed circuits 107. The upper flexible printed circuits 103 and the bottom flexible printed circuits 107 have conducting points respectively. Each conducting point located on the upper flexible printed circuit 103 corresponds with a conducting point located on the bottom flexible printed circuit 107, and the conducting points can contact each other via a corresponding through-hole formed in the separating sheet 105. Each of the through-holes and two corresponding conducting points is aligned with a keycap. For example, the conducting point 119a located on the upper flexible printed circuit 103 and the conducting point 119b located on the bottom flexible printed circuit 107 may contact via the through-hole 105a formed in the separating sheet 105. Each of the elastic elements 101 may be a block of elastic material beneath the keycap, for example a block of rubber, and has a protuberance 101a aligned with a through-hole 105a and the corresponding conducting points 109a and 109b. When the keycap is pressed to push the elastic element 101 downward, the protuberance 101a pushes the corresponding conducting point 109a through the through-hole 105a and makes electrical contact with the conducting point 109b to generate an electrical signal.
FIG. 2 is an exploded diagram of a keycap structure within a prior art keyboard. The keycap structure further comprises a supporting unit that is shaped like a pair of scissors or a bridge. For example, the scissors-shaped supporting unit is composed of a first supporting plate 213 and a second supporting plate 215 that are assembled to support the elastic elements 101 and connect a keycap 200 to the corresponding piezoelectric structure beneath the elastic elements 101.
However, using the scissors-shaped supporting unit not only expends much material and assembly time but also occupies significant space, space that customers demand to be as small as possible. Therefore, it is desirable to provide a thin keyboard structure that can be assembled easily and costs less to manufacture than the prior art.